1. Field of the Invention
The invention relates to a solar battery which is used in various power sources and, more particularly, to an integrated type solar battery in which a plurality of solar batteries are serially connected. The invention further relates to an integrated type solar battery using a thin film semiconductor.
2. Related Background Art
Generally, in the case of using a solar battery as a power source, a practical output voltage is not obtained when only a single solar battery element is used. Therefore, a plurality of solar battery elements are serially connected together. The serial connection of solar battery elements is a common feature irrespective of the kind of semiconductor material of the solar battery.
For instance, in a prior art solar battery using monocrystalline or polycrystalline silicon as a semiconductor layer, as shown in FIG. 6, adjacent solar batteries 601 and 602 are serially connected by connecting a collecting electrode 603 of one of the solar batteries 601 and the back surface of a wafer of the other solar battery 602 by lead wires 604. According to the above method, however, there is a problem in that electrical output is lost by the shadowing of the lead wires 604 which are connected to the collecting electrode 603. Also, since the lead wires are connected to the back surface of the wafer and the front and back surfaces of the wafer are coated with a resin, there are also problems such that the assembling steps are complicated and the manufacturing costs are high.
As a solar battery using a conductive substrate and an amorphous material as a semiconductor layer, there is known a solar battery in which a plurality of solar batteries are serially connected by using lead wires 705 as shown in FIG. 7. For example, a collecting electrode 703 of one (e.g., 701) of adjacent solar batteries 701 and 702 is connected to an edge portion 707 of the substrate of the other solar battery (e.g., 702) by the lead wires 705. In this case, however, there is also a problem in that electrical output is lost by the shadowing of the lead wires 705. There is also concern that edge portions 708 and 709 of the conductive substrate are short-circuited or the substrate edge portions 708 and 709 and the lead wires 705 are short circuited.
On the other hand, in a solar battery formed on an insulative substrate made of glass or the like by using an amorphous semiconductor material, there is known a method of serially connecting a plurality of solar batteries on an integrated substrate without using any lead wire.
As shown in FIG. 8, there is illustrated a solar battery wherein boundary portions of solar battery elements which are obtained by dividing a solar battery into a plurality of portions on a common substrate 801, an upper electrode 804 of one of the solar battery elements is connected to a lower electrode 805 of the adjacent solar battery element, thereby serially connecting the solar battery elements. According to this method, electric power is not lost by the shadows of lead wires. By optimizing the width of the solar battery elements between the connecting portions, electric power loss due to the resistance of transparent electrodes 802 and 805 and reduction of the light receiving area by the connecting portions can be decreased. According to the above method, however, since the lower electrodes 802 and 805, etc, semiconductor layers 803 and 806, etc, and upper electrodes 804 and 807, etc. must be individually patterned, there are problems such that the number of steps is large and the manufacturing costs rise. On the other hand, by increasing the light receiving area by narrowing the width of the connecting portion, the line width of patterning is narrowed. Therefore, there are problems such that the positioning accuracy of the patterning must be increased and the manufacturing apparatus becomes expensive. Further, according to the patterning method, there are problems such that the insulation of the connecting portion is insufficient and leakage current easily occurs. The above method is disclosed, for example, in JP-B-62-5353.